1. Field of the Invention
The present invention relates to deburring machined workpieces, and, more particularly, to a method and apparatus for deburring nonmetallic machined components of medical devices.
2. Description of the Related Art
Medical devices such as, e.g., a prosthetic knee or hip include components formed by and/or engraved by machining. Additional medical products formed by machining include, e.g., nonmetallic screws. These products can be formed from a plastic such as polyethylene, or, more specifically, ultra heavy molecular weight polyethylene. Machines, such as, e.g., a mill or a lathe are utilized to efficiently produce these products.
Machining generally produces a workpiece having burrs which must be removed. Machined screws generally have burrs, e.g., in the screw slot. FIG. 2 illustrates screw 20 including burrs 32. Burrs 32 may be formed at various locations in machined workpieces and are shown in slot 26 of screw 20 for illustrative purposes only. Additionally, as mentioned above, information is sometimes engraved on components of medical devices. Engraving can leave minor imperfections and debris which must be removed. For example, the under surface of a polyethylene tibial bearing component often has machined features as well as engraving.
Machined metal parts may be deburred, e.g., with a wire brush, or a grinding stone. Machined metal parts may also be deburred in a vibratory tumbler. The machined metal parts are loaded into the tumbler together with abrasive stones in a liquid (e.g., soap solution) medium. The tumbler is actuated and the parts are deburred through interaction with the abrasive stones. The deburring techniques utilized with metal parts cannot be used with machined plastic parts since these operations would cause significant scarring to a plastic part. A tumbling process cannot be used with plastic parts both because it will scar the parts and because it will impinge foreign materials on the parts.
Prior to use, debris and imperfections such as burrs must be removed from a machined workpiece. Machined nonmetallic workpieces are typically collected at the forming location and transported to an alternative location for cleaning and deburring. With the limitations of the above-mentioned metal deburring techniques in mind, cleaning and deburring of machined nonmetallic workpieces is typically done by hand with a cutting tool such as, e.g., an EXACTO knife or a scalpel together with tweezers. Deburring procedures of this type are time consuming, tedious to perform, and do not produce uniformly shaped workpieces. Additionally, this deburring technique is ineffective in removing fine imperfections in the workpiece such as hairlike burrs (a.k.a. xe2x80x9cwhiskersxe2x80x9d) and is hard on the operators who frequently receive nicks and cuts on their hands and fingers.
While mechanical deburring of a nonmetallic workpiece with a stiff bristled brush comprises an available alternative, this procedure suffers significant drawbacks. Application of a stiff bristled brush to a nonmetallic workpiece causes significant scarring of the workpiece and, therefore, cannot effectively be employed.
What is needed in the art is a method and apparatus for deburring a nonmetallic workpiece which yields uniformly shaped parts, decreases the time required for the deburring process, and is not harmful to the operator.
The foregoing shortcomings of the prior art are addressed by the present invention. The present invention utilizes a deburring material of sufficient hardness to debur a nonmetallic workpiece without scarring thereof. The deburring material is actuated and applied to a workpiece to effect deburring thereof. When the deburring material is applied to the workpiece, burrs thereon frictionally engage the deburring material. The deburring material has a durometer hardness and consequently a coefficient of friction whereby the frictional engagement of the burr with the deburring material is stronger than the attachment of the burr to the workpiece and therefore the burr is removed as the deburring material is actuated. An acceptable deburring material will have sufficient frictional characteristics to effect deburring as described above, and will have a durometer hardness such that application of the deburring material to the workpiece will not cause scarring of the workpiece. In one exemplary embodiment, the deburring material has a durometer hardness of 40.
In one exemplary embodiment, the present invention utilizes a deburring tool adapted for use with a mechanical actuating device and which includes deburring material affixed thereto. The deburring tool can be positioned as a tool in a CNC lathe which forms the part to be deburred. In this configuration, deburring occurs at the forming station. In one form of the current invention, the deburring material comprises polyisoprene. Polyisoprene is commercially available from, e.g., WARCO (West American Rubber Co., Inc.). One acceptable polyisoprene is 40-R-526 available from WARCO.
The invention, in one form thereof, comprises a deburring tool including an arbor and a disk affixed to the arbor. The disk is formed of a material of sufficient hardness to debur a nonmetallic workpiece without scarring the workpiece.
The invention, in another form thereof, comprises a deburring tool including a support structure with a deburring material affixed thereto. The deburring material is of sufficient hardness to debur a nonmetallic workpiece without scarring the workpiece.
The invention, in another form thereof, comprises a deburring tool having a deburring surface formed from a material of sufficient hardness to debur a nonmetallic workpiece without scarring the workpiece and an actuating means for actuating the deburring surface.
The invention, in another form thereof, comprises a method of deburring a machined workpiece. The method of this form of the current invention comprises the steps of: providing a deburring surface formed from a material of sufficient hardness to debur a nonmetallic workpiece without scarring the workpiece, and rubbing the machined workpiece with the deburring surface.
An advantage of the present invention is the ability to debur a nonmetallic workpiece in a quick and efficient manner.
Another advantage of the present invention is the ability to form substantially uniform nonmetallic workpieces utilizing a machining process.
A further advantage of the present invention is the ability to remove fine imperfections in machined workpieces.
Yet another advantage of the present invention is the ability to debur a workpiece without risking injury to the individual performing this task.
Yet a further advantage is the ability to mechanically debur a nonmetallic workpiece at the forming station and thereby decrease the required floor space to form and debur a product.